Astronomy and Astrophysics – Astronomy
Scientific paper
Nov 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997arep...41..802m&link_type=abstract
Astronomy Reports, Volume 41, Issue 6, November 1997, pp.802-812
Astronomy and Astrophysics
Astronomy
3
Scientific paper
The spectrophotometric (1200-7500 Angstroms) and photometric (UBVJHKL) observations of the classical symbiotic star YY Her both during its quiescent state and during a strong outburst in 1993 are presented. It is shown that the hot component of YY Her ionizing the circumstellar envelope and contributing appreciably to the UV continuum of the star cannot always be represented as a spherically symmetric radiative source similar to the hot component of a symbiotic nova. Occasionally, a warm (~1.5 x 10^4 K) nonspherical radiation source (probably an accretion disk), which markedly affects the shape of the star's continuum energy distribution in the long-wavelength part of the UV range, is added to the emission of a hot (~10^5 K) subdwarf in YY Her. Its appearance and relative intensity do not depend unequivocally on the total UV flux from the star. Forexample, in December 1981 and in June 1993 its contribution to the observed bolometric flux from the hot component was ~ 15% at U ~ 13.2 and U ~ 11.6, respectively, while in August 1980 it was not noticeable at U ~ 13.6. During the strong outburst in 1993, the bolometric flux from the hot component increased by a factor of >= 6, whereas the temperature of the hot subdwarf decreased from ~1.1 x 10^5 K to ~8.2 x 10^4 K. In December 1981, after a short-duration outburst of YY Her, the appearance of a substantial amount of neutral hydrogen was noted on the line of sight from the hot component to the observer which manifested itself in its characteristic dimming at Lambda < 1300 Anstroms. The minimum bolometric flux from the hot subdwarf is a factor of ~2 lower than the bolometric flux from its cool companion.
Kolotilov Eugenii A.
Munari Ulisse
Popova A. A.
Yudin Boris F.
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